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How to measure a roof for shingles

Before you can start your roofing project, you’ll need to know how much materials you’ll need—namely shingles. How much shingles you need depends on the size of your roof.

How do I calculate the size of my roof area?

We hope you enjoyed geometry class growing up, because you’ll need it.

Thankfully, most roofs are gable roofs—which means they consist of rectangular sections of shingles (as opposed to a more complex roof like a hip roof, which is triangular).

To calculate the size of your roof, you have a couple options.

If you’re okay with climbing onto your roof:

  1. Grab a ladder and climb up onto your roof
  2. Measure the length and width of each plane. Make sure to measure any dormers separately.
  3. Multiply roof length times width, then add them all together. That’s the total area of the roof, in square feet.


Materials needed:

  • Ladder
  • Measuring tape
  • Calculator


If you’d rather not climb onto your roof:

  1. Measure out the dimensions of the base of the house
  2. Check to see if the eaves of your roof planes extend out beyond the base of the house (i.e. overhangs). Measure that amount and add it to the length and/or width.
  3. Grab your ladder and climb to the edge of the roof to measure the roof pitch (or roof slope).
  4. Place your level against the roof and angle it so that the floating bubble is centered (i.e. so that it’s level).
  5. Measure the distance from the 12-inch mark of the level to the surface of the roof. This number, divided by 12, is your pitch (ex. a measure of 7 inches would mean a pitch of 7/12).
  6. Plug your dimensions and pitch into a pitch calculator to determine the size of your roof.
  7. Repeat this process for every rectangular section of your house to get your total roof area.

Materials needed:

  • Ladder
  • Tape measure
  • Level
  • Roofing calculator (online)


How do I figure out how many shingles I need?

Once you know the square footage of your roof, you’re ready to determine how many shingles you need to buy.


The standard unit of measurement for shingles is a roof “square”—which is actually 100 square feet (10 ft. x 10 ft.) of shingles.

So to determine number of squares you need, divide the total square footage of your roof by 100 (ex. – 3,000 sq. ft. / 100 = 30 squares of shingles).

A pro tip: budget about 10% of extra shingles to account for shingle waste due to trimming.


Roof shingles are sold by the bundle and by the square. The average asphalt shingle square weighs about 400 pounds, so roof squares are split up into smaller bundles of shingles.

The number of bundles can vary slightly based on the packaging, but typically it’s three bundles per square.

How do I estimate how much shingles will cost?

The cost of your roofing materials will vary by your shingle type and your location. But on average, here are the costs of the major shingle types:

  • Asphalt — $90 per roof square
  • Metal — $275-400 per roof square
  • Composite — $400 per roof square
  • Wood — $350-500 per roof square
  • Clay — $300-1000 per roof square


What are the basic tools and materials I need to install a new roof?

A list of tools and materials you could use to install a roof would be very long. But here are the basics for a standard installation of three-tab asphalt shingles on a residential roof.


  • Roofing nails
  • Roofing sealant
  • Self-adhesive waterproof underlayment
  • Flashing for vents and valleys
  • Drip edge
  • Asphalt shingles
  • No. 15 or No. 30 felt paper



  • Extension ladder
  • Roof harness
  • Chalk line
  • Caulk gun
  • Air hose or air compressor Hammer
  • Roofing stapler
  • Straight edge
  • Tin snips
  • Utility knife
  • Saw
  • Scaffolding and tarpaulin
  • Work gloves


How long should I expect a roof installation to take?

An experienced team of roofers can typically install a new roof on an average-sized home (i.e. 3,000 square feet of roof) in a day. But that can vary based on a variety of factors: size of your home, type of shingles, weather, and accessibility.

If you go the DIY route, you’re most likely looking at longer timelines—in some cases significantly longer. The timeline of a DIY roof installation can vary even more widely based on additional factors that include work and family schedules, expertise, manpower and more.

Should I re-roof my house or hire a contractor?

This is the age-old question homeowners face. One helpful way to think about it is in short-term and long-term costs.

The cost of hiring a roofing contractor are higher in the short-term but most likely lower (even zero) in the long-term—assuming you hire a quality roofing company.

The cost of doing it yourself is lower in the short-term but most likely higher in the long-term, since most people are not roofing experts and will make more mistakes.

So look at your budget and try to determine: How much are we willing/able to pay in the short-term? How much would we willing/able to pay in the long-term.

And one final consideration is, of course, time. Try to forecast realistically how much time you’ll need to complete the project with the manpower (or woman-power) you have available to you. What could be the relative cost of that time?

Need a roofer in Tacoma? Give us a call.

If you come to the conclusion that you do need to hire a roofing professional, give us a call at ACME Roofing. We’d be honored to be considered and pride ourselves on doing the job right—so that you don’t need to call us for another 30 years!